Climate- and Human-Induced Vegetation Changes in Northwestern Turkey and the Southern Levant since the Last Glacial

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Climate- and Human-Induced Vegetation Changes in Northwestern Turkey and the Southern Levant

since the Last Glacial

Dissertation

zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn

vorgelegt von Andrea Miebach

aus Bergisch Gladbach

Bonn, 2016

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Angefertigt mit Genehmigung der Mathematisch Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn

1. Gutachter: Prof. Dr. Thomas Litt 2. Gutachter: Prof. Dr. Dietmar Quandt Tag der Promotion: 27.01.2017

Erscheinungsjahr: 2017

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Contents 5

Summary

Northwestern Turkey and the southern Levant are key regions for studying vegetation and climate developments during migration phases of modern humans and the origin and expansion of agriculture.

Both regions have a long history of different anthropogenic occupation phases, and the vegetation was sensitive to climate variations and anthropogenic influences. However, paleoenvironmental conditions in northwestern Turkey and the southern Levant are still insufficiently understood. Therefore, the main aim of this doctoral thesis was to investigate climate- and human-induced vegetation changes in both regions during the Last Glacial and Holocene.

To fulfill this aim, palynological studies at three lacustrine archives were conducted. Pollen, non-pollen palynomorphs such as green algae and spores, and microscopic charcoal were extracted from sediment cores and microscopically analyzed. The sediment cores originated from Lake Iznik (northwestern Turkey), the Sea of Galilee (Lake Kinneret), and the Dead Sea (both southern Levant).

Pollen data inferred from Lake Iznik sediments reveal the vegetation pattern in northwestern Turkey during the past 31 ka BP (thousand years before present). The vegetation changed between (a) steppe during stadials suggesting dry and cold climatic conditions, (b) forest-steppe during interstadials implying milder and more humid climatic conditions, and (c) oak-dominated mesic forest during the Holocene indicating warm and humid climatic conditions. A distinct succession of pioneer trees, cold temperate trees, warm temperate trees, and Mediterranean trees occurred since the Lateglacial. Rapid climate changes reflected in vegetation shifts correlate with Dansgaard-Oeschger events (DO-4, DO-3, and DO-1), the Younger Dryas, and most likely the 8.2 ka event. The distinction between climate- and human-induced vegetation changes is challenging during early settlement phases. Nevertheless, evidence for human activity consolidates since ca. 4.8 ka BP (Early Bronze Age). Forests were cleared, and cultivated trees, crops, and secondary human indicator taxa appeared. Subsequent fluctuations between extensive agricultural uses and regenerations of the natural vegetation occurred.

The palynological investigation at the Dead Sea provides insights into the vegetation history of the southern Levant between ca. 88 and 9 ka BP. The pollen record from the Sea of Galilee yields additional information for 28–22 ka BP, when the Sea of Galilee rose above the modern lake level and temporarily merged with Lake Lisan, the Last Glacial precursor of the Dead Sea. A mixture of Irano-Turanian steppe communities, Saharo-Arabian desert vegetation, and Mediterranean woodland components occurred in the Dead Sea region during the Last Glacial. Pollen proportions of these three biomes changed over time mainly in response to changes in effective moisture (available moisture for plants). During the early Last Glacial (marine isotope stage (MIS) 5b/a and early MIS 4), the amount of Saharo-Arabian desert components was higher relative to later phases indicating low effective moisture. An increased proportion of Irano-Turanian steppe vegetation and Mediterranean woodland elements during the late MIS 4, MIS 3, and MIS 2 suggest more effective moisture. MIS 2 was the coldest period of the investigated timeframe as indicated by a change in arboreal taxa. An assessment of the vegetation and climate gradients in the southern Levant during MIS 2 is possible by comparing the Sea of Galilee and Dead Sea pollen datasets. The well-dated and high-resolution pollen record from the Sea of Galilee suggests that steppe vegetation with dwarf shrubs, grasses, and other herbs predominated in northern Israel during 28–22 ka BP. In contrast to the Holocene, dense Mediterranean woodland did not cover

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the surroundings of the Sea of Galilee. Thermophilous trees were probably patchily distributed in the whole study area. The gradient of effective moisture between the Sea of Galilee and the Dead Sea/Lake Lisan was not as strong as today. The Dead Sea region witnessed several environmental changes during the Lateglacial and early Holocene caused by climatic variations and/or anthropogenic influences. After these rapid and pronounced changes, a considerably different ecosystem with sparse Mediterranean woodland, high fire activity, and strong catchment erosion prevailed in the Dead Sea region.

While the results for northwestern Turkey are largely in line with previous regional vegetation and climate studies, previous investigations from the southern Levant concluded contrasting environmental scenarios for the Last Glacial and early Holocene. Thus, the new palynological results for the southern Levant apparently contradict some of the previous hypotheses. Therefore, factors influencing the pollen assemblage and the plant cover are discussed.

The three palynological investigations provide insights into long-term and short-term variations of the paleoenvironment in northwestern Turkey and the southern Levant since the Last Glacial. They contribute to our understanding of interactions between vegetation, climate, and humans in the Eastern Mediterranean. This knowledge is not only essential for reconstructing the migration history of modern humankind but also helps to evaluate effects of current and future climate changes on the environment.

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1 General Introduction

1.1 Background

This doctoral thesis is affiliated to the Collaborative Research Centre (CRC) 806 “Our way to Europe”

funded by the German Research Foundation. The CRC 806 investigates the interaction between past environmental conditions (e.g., climate and vegetation), cultural changes, and the mobility of anatomically modern humans (Homo sapiens sapiens). It uses an interdisciplinary approach combining archaeology and geosciences to capture the complexity of various research fields, methods, and concepts. The CRC 806 concerns the last 190 ka BP (kilo years before present; all radiocarbon dates in this chapter have been calibrated), the interval between the dispersal of modern humans from East Africa and the permanent establishment of Homo sapiens sapiens in Central Europe. It focuses not only on the primary expansion of modern humans towards Europe but also on secondary expansions and retreats of modern man along the dispersal corridors. The CRC 806 covers various projects grouped in clusters with different spatial focuses: A) the source region in East Africa, B) the eastern trajectory via the Near East and the Balkans, C) the western trajectory via North Africa and the Iberian Peninsula, and D) the sink region in Central Europe (Richter et al., 2012b).

The western trajectory is a possible corridor. Investigations try to answer whether the strait of Gibraltar was a barrier or bridge between North Africa and the Iberian Peninsula for human dispersal. In contrast, the eastern trajectory (cluster B) was the principal corridor of human dispersal (Richter et al., 2012b).

Major dispersal events took place at the eastern trajectory. Firstly, the initial dispersal of Homo sapiens sapiens out of Africa. The earliest representatives of modern humans outside Africa are skeletons from the Israeli cave sites Qafzeh and Skhul, which were dated to 120–90 ka BP (Richter et al., 2012a and references therein). Secondly, the reoccupation of the Near East during the Last Glacial. Earliest fossil evidence is provided by skeletal material from Manot Cave, Israel, dating back to ca. 55 ka BP (Hershkovitz et al., 2015). And thirdly, the spread of agriculture and husbandry from the Near East to Central Europe during the Holocene. Clear evidence of agriculture and domestication of several animals goes back to about 11 ka BP in the so-called Fertile Crescent (Miller, 1991; Shea, 2013). Still, only little is known about the detailed framework of environmental conditions during these important dispersal processes.

Project B3 of cluster B focuses on environmental responses to climate impacts in the southern Levant (geographical area in the southeastern Mediterranean region). The southern Levant is a key region for studying the relationship between cultural and environmental changes. It has a long archaeological record not only with fossils and artefacts of modern humans but also of Neanderthals (Shea, 2008 and references therein). The region is regarded as a possible meeting point where gene flow between early modern humans and Neanderthals could have occurred (Kuhlwilm et al., 2016). Today, the southern Levant is a transitional area of different climate and vegetation zones: subhumid Mediterranean woodland, semiarid steppe, and arid desert (Zohary, 1962). The occurrence of different vegetation types within a small region makes the southern Levant a sensitive region for reconstructing climate changes in the past. The Dead Sea is a key archive for investigating the 220 ka old history of climate and vegetation change in the southern Levant (Neugebauer et al., 2014; see chapter 4). Together with a

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sediment profile from the nearby Sea of Galilee (Hazan et al., 2005), the detection of environmental gradients is possible (see chapter 3 and 4).

Project B4 of cluster B concerns the climatic evolution of the Marmara Region during the past 50 ka.

The Marmara region, surrounding the Marmara Sea in northwestern Turkey, is situated at an important bottleneck for human migration. Of particular interest are the following intervals: firstly, the Lateglacial when human habitats reestablished after the Last Glacial Maximum (LGM) and secondly, the early and middle Holocene when farming and husbandry dispersed from the Near East to Central Europe (Richter et al., 2012b). A key archive for investigating the regional environmental development is Lake Iznik, the largest lake in the Marmara region. Its sedimentological, geochemical, and biological (e.g., pollen) composition enables the reconstruction of the paleolimnology, paleovegetation, and paleoclimate of the past 31 ka (Roeser et al., 2012, 2016; Ülgen et al., 2012; see chapter 2).

The investigation of the paleoenvironment, particularly the vegetation and climate, in the Eastern Mediterranean is not only substantial to understand the history of humankind but also to evaluate climate changes in the past. Understanding the nature of climate variations in the past and its influences on the environment is crucial to predict impacts of recent and future climate changes. While instrumental and historical climate records are only available for the last few centuries, paleoclimatic proxy data are necessary to understand Earth system feedbacks and climate variations on a longer timescale (Schönwiese, 2008; Masson-Delmotte et al., 2013). According to the latest Intergovernmental Panel on Climate Change Assessment Report (IPCC, 2013), concentrations of greenhouse gases have excessively increased, the Earth’s surface temperature has unprecedentedly became warmer, and the sea level has risen during the last decades. Moreover, precipitation rates in the Eastern Mediterranean have decreased.

With the help of climate models, implications of recent and future climate changes can be predicted.

Even under different scenarios of anthropogenic forcings, climate models predict a further rise in temperature and a further decrease in precipitation in the Eastern Mediterranean until the end of the 21^st century.

To reveal the vegetation and climate history, palynology is a powerful technique. Palynology is the study of pollen and other microscopic organic-walled particles, so called non-pollen palynomorphs (NPPs), such as spores and algae. Seed plants produce pollen grains (male microgametophytes) in great abundance for reproduction. Pollen grains are usually dispersed by wind, water, or animals to pollinate other plants (Faegri and Iversen, 1989). However, particularly wind-transported pollen grains often do not reach the plants but deposit in the landscape. Lakes are natural pollen traps in terrestrial environments. They receive water and sediments from the catchment area, which usually also contain pollen grains. Other pollen grains directly reach the water surface or are produced by local aquatic plants growing in the water. Pollen grains and other sediment components deposit successively on the lake bottom (Moore et al., 1991). Pollen grains have a resistant coat (exine) made of sporopollenin. Under appropriate conditions, the exine can be preserved up to millions of years (Straka, 1975).

Nowadays, lacustrine sediments can be recovered by drilling. Sediment profiles are correlated in time with the help of dating techniques and age-depth models. Sediment samples from drilling cores are processed in laboratories to extract palynomorphs from the sediment. Pollen grains, which are specific to plant families, genera, or even species, and NPPs can be microscopically identified. By counting a statistically robust number of pollen and NPP types per sample along the sediment profile, developments

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in the environment, particularly the vegetation, can be reconstructed. However, the proportion of each pollen type depends not only on the number of parent plants but also on their pollen productivity, pollen transport, and preservation conditions. Hence, the counted pollen assemblage is an indirect record of the local and regional vegetation and needs to be interpreted. Nevertheless, pollen and NPPs provide valuable information about the history of the lake, the surrounding vegetation, and possible human impacts on the paleoenvironment (Faegri and Iversen, 1989; Moore et al., 1991). Pollen data can also be used to reconstruct the regional climate history because the occurrence and frequency of plants strongly correlate with the regional climate (Birks et al., 2010). In contrast to macrofossil remains, pollen grains are produced in high amounts and are widely spread. This provides the opportunity not only for qualitative but also quantitative vegetation and climate reconstructions (Faegri and Iversen, 1989). The processed sediment samples often additionally contain microscopic charcoal, which can be used to reconstruct fire regimes in the past (Whitlock and Larsen, 2001).

1.2 Current state of knowledge

Several global and northern hemispheric climate changes affected the Eastern Mediterranean region during the Quaternary. These climate changes were of long-term or short-term kind. Long-term climate variations were triggered by calculable orbital parameters affecting the insolation on the Earth (Fig.

1.1c) and resulting in the so-called Milankovitch cycles (Hays et al., 1976; Berger, 1978). Those climatic cycles composed of cold stages (glacials) and warm stages (interglacials). Each glacial-interglacial cycle of the late Quaternary encompassed averagely 100 ka (Lowe and Walker, 2015). Imprints of long-term climate changes are for example represented by marine isotope stages (MIS), which can be derived from oxygen isotope (δ¹⁸O) records of benthic foraminifera. Changes in benthic δ¹⁸O were related to temperature, global ice volume, and water salinity (Lisiecki and Raymo, 2005; Fig. 1.1a). MIS 1 corresponds to the current interglacial, the Holocene (Sanchez Goñi and Harrison, 2010). The Last Glacial has been either defined as the period corresponding to MIS 4–2 (Sanchez Goñi and Harrison, 2010) or MIS 5d–2 (Dansgaard et al., 1993; Litt, 2007).

Several rapid short-term climate changes occurred during the Last Glacial. Interstadials were warm phases within a glacial that were either too short or cold to reach the climatic conditions of an interglacial (Jessen and Milthers, 1928). Interstadials are also described as Dansgaard-Oeschger (DO) events (Dansgaard et al., 1982; Rasmussen et al., 2014) and are associated with an abrupt warming followed by a gradual re-cooling. They are well documented in high-resolution Greenland ice core records (e.g., NGRIP members, 2004; Fig. 1.1b). 25 DO events occurred during the Last Glacial (MIS 5d–2). Their duration varied from centuries to several millennia (Rasmussen et al., 2014). Stadials were cold phases within a glacial. One of the coldest phases was the Last Glacial Maximum (LGM) when global ice volume maximized at 23–19 ka BP (Mix et al., 2001). Other very pronounced cold phases are associated with Heinrich events when ice-rafted debris deposited in the North Atlantic caused by massive discharges of icebergs (Heinrich, 1988; Bond et al., 1992; Fig. 1.1b: H1–H10). Subsequently, the Atlantic thermohaline circulation broke down (Broecker and Hemming, 2001; Rahmstorf, 2002).

Climatic imprints related to Heinrich events are documented in many northern hemispheric records (e.g., Hemming, 2004; Robinson et al., 2006).

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Figure 1.1: Paleoclimate records: a) LR04 benthic δ¹⁸O stack and derived marine isotope stages (MIS; Lisiecki and Raymo, 2005); b) Greenland δ¹⁸O record (NGRIP members, 2004) with numbered Dansgaard-Oeschger events (above; Rasmussen et al., 2014) and Heinrich events (below; Rasmussen et al., 2003); c) Summer and winter insolation for the 30^th parallel north (Berger and Loutre, 1991).

Insights into the local and regional paleoenvironmental conditions of the Eastern Mediterranean have been gained by various investigations of different disciplines. Among these investigations were for instance lake level reconstructions (e.g., Bartov et al., 2003), climate reconstructions based on tree rings (e.g., Touchan et al., 2007), geochemical investigations of loess deposits (e.g., Obreht et al., 2015), and marine isotope records (e.g., Cheddadi and Rossignol-Strick, 1995; Almogi-Labin et al., 2009).

Different methods were used to reveal the local or regional paleovegetation of the Eastern Mediterranean including macrofossil analyses, i.e. the study of macroscopic plant remains such as seeds, fruits, and leaves (e.g., Marinova and Atanassova, 2006), phytolith analyses, i.e. the study of siliceous plant remains (e.g., Turner et al., 2010), and carbon isotope (δ¹³C) analyses of speleothems (e.g., Frumkin et al., 2000; Vaks et al., 2006). Measurements of δ¹³C mainly mirror the ratio of C3 plants to arid-adapted C4 plants as well as the vegetation density overlying the cave. But δ¹³C can also be influenced by other factors (Bar-Matthews et al., 1997; Frumkin et al., 2000). The most common method to study the paleovegetation of the Eastern Mediterranean is the pollen analysis. The study of fossil pollen is the only quantitative method that provides a continuous and adequate representation of vegetation changes in the past (Faegri and Iversen, 1989; Moore et al., 1991; Sadori et al., 2016). In addition to pollen, palynological analyses provide microscopic charcoal and NPPs such as dinoflagellates and green algae, which supported the reconstruction of paleoenvironmental conditions of the Eastern Mediterranean in previous studies (e.g., Shumilovskikh et al., 2014; Pickarski et al., 2015).

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Previous palynological studies from the Eastern Mediterranean and Near East documented long-term vegetation changes in response to glacial-interglacial cycles. The majority of these investigations agreed on variations between forest expansion during interglacials and a dominance of open, steppic vegetation during glacials. However, strong spatial differences in vegetation density and plant composition prevailed (e.g., Tzedakis et al., 2006; Litt et al., 2014; Sadori et al., 2016). Moreover, many pollen records mirror vegetation changes in response to short-term climate oscillations. DO events, i.e. rapid warming events, were frequently identified in pollen studies from the northeastern Mediterranean and Near East. Those investigations indicated a spread of woody taxa, although woodland intensities differed from region to region (e.g., Fletcher et al., 2010; Müller et al., 2011; Panagiotopoulos et al., 2014;

Pickarski et al., 2015). The effect of DO events on the vegetation in the Levant is less clear. This might be partly caused by a low data resolution or chronological uncertainties (cf. Niklewski and Van Zeist, 1970; Cheddadi and Rossignol-Strick, 1995). Most pollen records from the Eastern Mediterranean and Near East do not indicate a clear vegetation response related to Heinrich events, i.e. harsh stadial conditions (e.g., Tzedakis et al., 2004; Shumilovskikh et al., 2014). In areas where tree populations were already close to their climatic tolerance limit, differences between pronounced Heinrich Stadials and other stadials might not be recorded. Even moderate stadial conditions could have crossed the ecological threshold for tree growth (Tzedakis et al., 2004). However, Langgut et al. (2011) suggested distinct vegetation responses associated with Heinrich events inferred from a marine pollen record from the Levantine Basin.

Fig. 1.2 shows the location of long marine and lacustrine pollen records in the Eastern Mediterranean and Near East. The largest density of long pollen records occurs on the Balkan Peninsula. Here, the longest continuous pollen record from the Eastern Mediterranean, namely the pollen record from Tenaghi Philippon, Greece, spanning 1.35 million years, has been obtained (e.g., Tzedakis et al., 2006).

Other palynological studies that reach further back in time than the Last Glacial took place at Lake Ohrid (Macedonia/Albania, 500 ka, e.g. Sadori et al., 2016), Lake Prespa (Macedonia/Albania/Greece, 92 ka, e.g. Panagiotopoulos et al., 2014), Ioannina (Greece, 130 ka, e.g. Tzedakis et al., 2002), and Kopais (Greece, 130 ka, e.g. Tzedakis, 1999). Investigations of the vegetation history at the Greek sites of Xinias and Megali Limni encompassed major parts of the Last Glacial and Holocene (e.g., Digerfeldt et al., 2000; Margari et al., 2009). Marine cores from Marmara Sea and Black Sea provided records for the last 34 and 64 ka, respectively (Mudie et al., 2002; Shumilovskikh et al., 2012, 2014; Valsecchi et al., 2012). Marine and terrestrial vegetation studies differ from each other. Firstly, marine records usually represent a very large vegetation signal because the pollen source area is positively related to the archive size (Jacobson and Bradshaw, 1981). And secondly, pine pollen are usually greatly overrepresented in marine sediments (Faegri and Iversen, 1989). However, long terrestrial pollen records from Anatolia were almost lacking. The only previous long pollen record originated from Lake Van in Eastern Anatolia (E Turkey, 600 ka, e.g. Litt et al., 2014). In its vicinity, two additional terrestrial archives that were used for paleovegetational studies exist: Lake Urmia (NW Iran, 200 ka, e.g. Djamali et al., 2008) and Lake Zeribar (W Iran, 45 ka, e.g. van Zeist and Bottema, 1977).

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Figure 1.2: Location of long pollen records in the Eastern Mediterranean/Near East (with adequate chronologies and resolution). Blue: previous pollen records encompassing at least the last 70 ka (MIS 4–1). Black: previous pollen records encompassing at least the last 30 ka (MIS 2–1). Red: pollen records of this study.

Several palynological studies took place in the Levant. Four marine cores from the Levantine Basin are available and encompass the past 70 to 250 ka. They represent a huge pollen source area due to the basin size, and they were influenced by pollen brought by the Nile, particularly during glacial periods when the sea level was lower (Cheddadi and Rossignol-Strick, 1995; Langgut et al., 2011). Various terrestrial paleovegetational studies took place in the Levant during the 1960s to 1990s. According to these studies, several pollen records encompass partly or completely the Last Glacial and Holocene (e.g., Ghab Valley, Niklewski and Van Zeist, 1970; Sea of Galilee, Horowitz, 1971; Birkat Ram, Weinstein, 1976; Dead Sea, Horowitz, 1979; Hula Basin, Weinstein-Evron, 1983). Based on available pollen data, Horowitz (1992) presented a vegetation model for northern Israel and the Dead Sea region. This model suggests a predominance of Mediterranean forests in northern Israel during the Last Glacial (MIS 4–2) and a considerable reduction of Mediterranean forests and spread of steppe during interglacials (MIS 5 and 1). For the Dead Sea region, the model suggests a spread of Mediterranean woodland during MIS 4 and 2, and the occurrence of steppe and desert vegetation during MIS 5, 3, and 1. These hypotheses were in line with climatic interpretations of other investigations such as lake level reconstructions, but they contrasted pollen studies from other parts of the Eastern Mediterranean. However, the sedimentary sequences used for pollen analyses in the southern Levant were mostly sparsely dated and following studies questioned some chronologies (e.g., Rossignol-Strick, 1995; van Zeist et al., 2009). In addition, those previous pollen records were often of low resolution, or pollen counts were statistically not reliable. Subsequent long terrestrial Levantine pollen records have been obtained from Yammouneh

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(Lebanon, 400 ka, e.g. Gasse et al., 2015) and Birkat Ram (N Israel, 30 ka, e.g. Schiebel, 2013). They are chronologically better constrained and of higher resolution. Both pollen records suggest contrasting vegetation developments, namely the predominance of Mediterranean forests during interglacials and the occurrence of steppe vegetation during glacials. However, during glacial periods, these sites were probably influenced by orographic effects given the high altitudes (cf. Develle et al., 2011). The vegetation at lower altitudes might have differed considerably.

During the Holocene, the Eastern Mediterranean environment was more and more influenced by anthropogenic impacts. On the one hand, this made it more difficult to clearly ascribe vegetation changes identified in pollen records to climate variations, particularly during the late Holocene (e.g., Roberts, 1990; Wick et al., 2003). On the other hand, it allowed to study influences of humans on the ecosystem and enabled the comparison of palynological investigations to archaeological records (e.g., Bottema et al., 2001; Shumilovskikh et al., 2016). Signs of cereal cropping, fruticulture, grazing, and forest clearance were traced in palynological assemblages (e.g., Behre, 1990; Bottema and Woldring, 1990).

In addition, secondary impacts of human activities such as increased erosion rates and altered fire regimes were identified (e.g., Eastwood et al., 1998; Quintana Krupinski et al., 2013). However, some difficulties to record prehistoric occupation phases in pollen records from the Near East compared to other regions, e.g. Central Europe, were described. Firstly, most cultivated species such as cereals and olive trees already occurred naturally in the Near East. Secondly, several secondary indicator species (non-cultivated plants that benefit from anthropogenic influences) were also common in the Near East before humans started to change their environments. And thirdly, the sensitivity of the vegetation to minor climate variations made a separation between anthropogenic and climatic influences difficult (Behre, 1990; Bottema and Woldring, 1990).

The timing and kind of human-induced alterations of the ecosystem depend on the regional and local settlement history. The southern Levant has a long archaeological record of different settlement phases.

Sedentism occurred already during the Last Glacial by Natufian people (Bar-Yosef, 1998) but anthropogenic activities amplified during the early Holocene. Plants such as cereals and pulses were cultivated and agriculture spread. Neolithic settlers domesticated animals such as sheep and goat and used them for pastoral farming. The regional population grew and sedentary village life emerged (Kuijt and Goring-Morris, 2002; Shea, 2013). By the ninth millennium BP, Neolithic farming communities reached northwestern Turkey (Özdoğan, 2011; Düring, 2013). Several important prehistoric settlements are situated near Lake Iznik, namely Ilıpınar, Hacılar tepe, Menteşe, and Barcın Höyük (Roodenberg and Roodenberg, 2008; Roodenberg et al., 2008). They provided insights into local settlement structures and the Neolithic way of life in the eastern Marmara region.

1.3 Aim and structure of this thesis

Previous pollen records from the Eastern Mediterranean and Near East showed the sensitivity of the vegetation to respond to long-term and rapid climate oscillations in the past. However, several differences between records occurred concerning (a) the registration of individual oscillations, (b) the magnitude of vegetation and climate changes, (c) the nature of vegetation and climate variations mirrored for instance in the vegetation composition, and (d) the length of recorded events (Fletcher et

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al., 2010; Sanchez Goñi and Harrison, 2010, see also section 1.2). Long Eastern Mediterranean pollen records with adequate chronologies and resolution that encompass the Last Glacial and Holocene are rare (Fig. 1.2). The lack of available data is particularly unfavorable in key regions of human history such as the Marmara region in northwestern Turkey and the southern Levant. The vegetation history in both regions is not sufficiently understood. Therefore, high-resolution pollen records with robust and independent chronologies are needed to reveal environmental conditions in the past.

To gain new insights into the vegetation history in relation to climate changes and anthropogenic influences of northwestern Turkey and the southern Levant since the Last Glacial, pollen spectra of lacustrine archives were investigated. This doctoral thesis presents these palynological investigations and aims to address the following objectives:

I) Kind and magnitude of long-term environmental changes:

The interpretation of pollen assemblages allows to reconstruct the paleovegetation and paleoclimate. NPP and microscopic charcoal data yield additional information about environmental conditions in the past. Palynology does not only help to understand the kind of changes, but as a quantitative method it also provides insights into the magnitude of changes (Faegri and Iversen, 1989; Moore et al., 1991; Whitlock and Larsen, 2001).

II) Detection of rapid vegetation and climate changes:

If the vegetation is sensitive enough, it responds to short-term and minor climate variations. Well- dated sediment sequences and high-resolution analyses give the opportunity to detect not only long-term variations but also rapid changes.

III) Regional vegetation and climate gradients:

By comparing pollen records between each other and with other paleovegetation and paleoclimate studies, the detection of regional vegetation and climate gradients is possible. Special emphasis is given to environmental gradients between the Sea of Galilee and Dead Sea.

IV) Detection and timing of human influences on the vegetation:

Since the neolithization (begin of agriculture, husbandry, and sedentary village life), human influences on their environment grew (Miller, 1991; Rollefson and Köhler-Rollefson, 1992). It is possible to detect anthropogenic influences in pollen and NPP profiles (Bottema and Woldring, 1990). The comparison with archaeological findings helps to distinguish between human- and climate-induced vegetation changes.

To address these objectives, three lacustrine archives were selected for palynological investigations.

These archives are particularly suitable because of the following criteria:

I) All of them are located on the eastern trajectory of modern human dispersal from East Africa to Europe. The Dead Sea and the Sea of Galilee are situated at the Dead Sea rift valley, a possible migration route of modern humans (Richter et al., 2012a). Lake Iznik is situated in the Marmara region, a bottleneck region for human migration between Anatolia and the Balkans (Richter et al., 2012b).

II) Important archaeological sites are in the vicinity of the lakes. The core from Sea of Galilee was directly drilled at the archaeological site of Ohalo II, which is a well-preserved Epipaleolithic fisher-hunter-gatherers site (Nadel et al., 1995). In addition, several archaeological sites are in Israel and Jordan, where remains of modern humans and Neanderthals are preserved (Shea, 2013).

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Several Neolithic settlements are in close proximity of Lake Iznik, e.g. the well-investigated site of Ilıpınar (Roodenberg and Roodenberg, 2008). This gives the opportunity for direct comparisons of biogeological and archaeological records.

III) The lacustrine archives are located at climate and vegetation transition zones. The southern Levant is marked by a steep gradient in precipitation resulting in the transition between (a) subhumid Mediterranean woodland in the north, (b) semiarid Irano-Turanian steppe vegetation in the center, and (c) arid Saharo-Arabian desert vegetation in the south (Zohary, 1962). Lake Iznik borders two vegetation zones, which result from the transition of Mediterranean climate and Pontic climate: (a) Mediterranean woodland and (b) Euxinian mesic deciduous and mixed forest (Zohary, 1973). This makes the archives particularly sensitive for the detection of climate changes in the past. Already weak climate variations probably resulted in shifts of vegetation boundaries and alterations of pollen assemblages.

IV) The selected archives are the largest lakes of the regions of interest. They mainly represent a regional instead of a local pollen signal because the pollen source area is positively correlated to the archive size (Jacobson and Bradshaw, 1981). Thus, the reconstruction of the regional vegetation and climate is possible.

V) Site surveys and previous palynological studies demonstrated the suitability of the archives for vegetation analyses in response to climate changes and human impacts (e.g., Litt et al., 2012;

Ülgen et al., 2012; Schiebel, 2013).

VI) However, previous palynological studies (with adequate chronologies and resolution) only encompassed parts of the Holocene. The timeframes of interest for the CRC 806 were not investigated yet.

This doctoral thesis describes three palynological studies based on lacustrine sediments of Lake Iznik, the Sea of Galilee, and the Dead Sea. The thesis provides new insights into the paleoenvironmental conditions in northwestern Turkey and the southern Levant since the Last Glacial. It reveals the paleovegetation in response to climate variations, human influences, and fire activity. In the future, the results can be used for quantitative climate analyses, predictions of recent and future climate changes, and evaluations of potential impacts on hominid population dynamics. The three palynological studies are presented in chapter 2–4. Each chapter gives an introduction by describing the specific background, previous investigations, and the aim of the study. Descriptions of each study area, the used material, the applied methods, and the results follow. The results are discussed with emphasis on temporal vegetation dynamics, their relation to short-term and long-term climate oscillations, and anthropogenic influences on the vegetation. The results are compared to other regional investigations such as pollen records, speleothem data, lake level reconstructions, and archaeological findings. Each chapter ends with a conclusion. Chapter 2 presents the palynological study of Lake Iznik. It is based on the following peer- reviewed publication:

Miebach, A.; Niestrath, P.; Roeser, P. & Litt, T. (2016): Impacts of climate and humans on the vegetation in northwestern Turkey: palynological insights from Lake Iznik since the Last Glacial.

Climate of the Past 12: 575–593. Doi:10.5194/cp-12-575-2016.

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The publication appears in this thesis in its original wording but with a slightly modified layout. Chapter 3 focuses on the palynological investigation at the Sea of Galilee. It is based on the following manuscript submitted for publication:

Miebach, A.; Chen, C.; Schwab, M. J.; Stein, M.; Litt, T. (2016): Vegetation and climate during the Last Glacial high stand (ca. 28–22 ka BP) of the Sea of Galilee, northern Israel. Quaternary Science Reviews: under review.

Chapter 4 deals with the palynological study of the Last Glacial and early Holocene Dead Sea entitled:

Last Glacial and early Holocene vegetation, climate, and fire history of the Dead Sea region inferred from palynological analyses.

It covers the timeframe between ca. 88 and 9 ka BP and connects to the Holocene pollen record published by Litt et al. (2012), which encompasses the last 10 ka BP. Chapter 4 will be submitted after performing some final analyses. Chapter 2–4 are conceptualized to allow an independent understanding. Chapter 5 is a synthesis of the three palynological studies. It addresses the four objectives of this doctoral thesis and summarizes the main conclusions of the three palynological investigations.

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Chapter 2 27

1 Chapter 2 is based on Miebach, A.; Niestrath, P.; Roeser, P. & Litt, T. (2016): Impacts of climate and humans on the vegetation in northwestern Turkey: palynological insights from Lake Iznik since the Last Glacial. Climate of the Past 12: 575–593. Doi:10.5194/cp-12-575-2016.

2 Impacts of climate and humans on the vegetation in northwestern Turkey: palynological insights from Lake Iznik since the Last Glacial

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2.1 Abstract

The Marmara region in northwestern Turkey provides a unique opportunity for studying the vegetation history in response to climate changes and anthropogenic impacts because of its location between different climate and vegetation zones and its long settlement history. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate-related changes of the lake level and the lake mixing. However, a palynological investigation encompassing the Late Pleistocene to Middle Holocene was still missing. Here, we present the first pollen record of the last ca.

31 ka cal BP (calibrated kilo years before 1950) inferred from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Our study reveals that the vegetation in the Iznik area changed generally between (a) steppe during glacials and stadials indicating dry and cold climatic conditions, (b) forest-steppe during interstadials indicating milder and moister climatic conditions, and (c) oak-dominated mesic forest during interglacials indicating warm and moist climatic conditions.

Moreover, a pronounced succession of pioneer trees, cold temperate, warm temperate, and Mediterranean trees appeared since the Lateglacial. Rapid climate changes, which are reflected by vegetation changes, can be correlated with Dansgaard-Oeschger (DO) events such as DO-4, DO-3, and DO-1, the Younger Dryas, and probably also the 8.2 event. Since the mid-Holocene, the vegetation was influenced by anthropogenic activities. During early settlement phases, the distinction between climate- induced and human-induced changes of the vegetation is challenging. Still, evidence for human activities consolidates since the Early Bronze Age (ca. 4.8 ka cal BP): cultivated trees, crops, and secondary human indicator taxa appeared, and forests were cleared. Subsequent fluctuations between extensive agricultural uses and regenerations of the natural vegetation become apparent.

2.2 Introduction

The reconstruction of past climatic and environmental conditions is crucial to understand the living conditions and migration processes of former societies. After the first spread of modern humans into Europe during the Last Glacial (e.g., Benazzi et al., 2011; Higham et al., 2011), different population dynamics into and out of Europe followed. These population dynamics also include the spatial expansion of farming and husbandry, which happened between ca. 11 600 and 5500 years ago. The Marmara region, situated between the Mediterranean Sea and the Black Sea at the principal corridor of human dispersal from Africa via the Middle East to the Balkans, functioned as an important bottleneck for all migrated societies (Richter et al., 2012).